What does over-the-horizon communication utilize for long-distance transmission?

Over-the-horizon communication is designed to transmit information over long distances beyond the line of sight, typically utilizing satellite links. This method leverages the capabilities of satellites that can relay signals between distant locations on Earth, effectively bypassing physical obstructions such as terrain or the curvature of the Earth.

Satellite communications involve sending signals to a satellite that is positioned in outer space, which then transmits the signals back down to a different location. This is particularly useful when traditional ground-based communication methods may be limited due to distance or obstacles, allowing for greater coverage and connectivity.

In contrast, high frequency waves, while capable of over-the-horizon communication, typically rely on ionospheric reflections, and are not as reliable for consistent long-distance communication as satellite technology. Visual signals are generally limited by range and environmental conditions, making them impractical for extensive communication needs. Underwater acoustics are primarily used for communicating underwater, such as in naval applications, and are not effective for long-distance terrestrial communication.

Thus, utilizing satellite links is the most effective and reliable method for achieving over-the-horizon communication in modern systems.